Ge掺杂碳化硅晶体的生长缺陷

采用物理气相传输法(PVT)制备了2英寸Ge掺杂和非掺SiC晶体, 并使用二次离子质谱仪(SIMS)、显微拉曼光谱(Raman spectra)仪、体式显微镜、激光共聚焦显微镜(LEXT)和高分辨X射线衍射(HRXRD)仪等测试手段对其进行了表征。结果表明, Ge元素可以有效地掺入SiC晶体材料中, 且掺杂浓度达到2.52×10¹⁸/cm³, 伴随生长过程中Ge组份的消耗和泄漏, 掺杂浓度逐渐降低; 生长初期高浓度Ge掺杂会促使6H-SiC向15R-SiC晶型转化, 并随着生长过程中Ge浓度的降低快速地转回6H-SiC稳定生长。用LEXT显微镜观察发现, 生长初期过高的Ge掺杂导致空洞明显增多, 位错密度增加, 掺杂晶体中位错密度较非掺晶体增大一倍。HRXRD分析表明掺Ge能增大SiC晶格常数, 这将有利于提高与外延III族氮化物材料适配度, 并改善器件的性能。     

铒镱共掺磷硅酸盐光纤的制备及其激光性能研究

利用改进化学气相沉积法(MCVD)的反向沉积工艺,结合无铝的溶液掺杂技术,制备了高性能掺磷石英基的铒镱共掺光纤.反向沉积技术表现出了在纤芯中大量沉积磷这类高温下极易蒸发成分上的优势.研究表明,这种光纤中,铒镱离子能量传递效率极高,掺磷的石英基质对于促进镱离子对铒离子的能量传递,抑制镱离子寄生荧光作用明显.最后,搭建了双包层铒镱共掺光纤激光器系统,在光纤长度为4 m时,获得了3.2 W的最大功率输出,斜率效率达30%.     

Tm^3＋-Yb^3＋共掺杂NaYF4蓝色上转换发光粉的合成及其性质研究

采用溶胶-凝胶（Sol—gel）法制备出2％Tm^3＋、0％～98％Yb^3＋（摩尔分数,下同）共掺杂NaYF4蓝色上转换发光粉。Yb^3＋共掺杂促进了Tm^3＋掺杂NaYF4由β相到α相的转变。在976nm半导体激光器（LD）激发下,在430-500nm和620-750nm范围内获得了蓝色和红色上转换发光。随着Yb^...     

Comparison of Ohmic contact resistances of n- and p-type Ge source/drain and their impact on transport characteristics of Ge metal oxide semiconductor field effect transistors

We report the results of a systematic study to understand low drive current of Ge-nMOSFET (metal-oxide-semiconductor field-effect transistor). The poor electron transport property is primarily attributed to the low dopant activation efficiency and high contact resistance. Results are supported by analyzing source/drain Ohmic metal contacts to n-type Ge using the transmission line method. Ni contacts to Ge nMOSFETs exhibit specific contact resistances of 10^− 3-10^− 5 Ω cm², which is significantly higher than the 10^− 7-10^− 8 Ω cm² of Ni contacts to Ge pMOSFETs. The high resistance of Ni Ohmic contacts to n-type Ge is attributed mainly to insufficient dopant activation in Ge (or high sheet resistance) and a high tunneling barrier. Results obtained in this work identify one of the root causes of the lower than expected Ge nMOSFET transport issue, advancing high mobility Ge channel technology.     

Ge掺杂MnTe材料的热电输运性能

MnTe作为一种新型的无铅p型热电材料, 在中温区热电领域具有广阔的应用前景, 但其本身的热电性能不足以与高性能n型热电材料相匹配。本研究通过真空熔炼-淬火和放电等离子烧结的方法制备不同Ge掺杂量的致密且均匀的Mn_1.06-xGe_xTe(x=0, 0.01, 0.02, 0.03, 0.04)多晶块体样品。过量的Mn可以有效抑制MnTe₂相, 提高基体相的热电性能。通过掺杂4%Ge粉末, 材料的载流子浓度提高到7.328×10¹⁸ cm^-3, 电导率在873 K增大到7×10³ S∙cm^-1, 功率因子提升至620 μW∙m^-1∙K^-2。同时, 通过点缺陷增强声子散射使材料的热导率降低到0.62 W∙m^-1∙K^-1, 实现了对材料电声输运性能的有效调控。Mn_1.02Ge_0.04Te在873 K获得了0.86的热电优值ZT, 较纯MnTe材料提高了43%。     

A~ⅢB~Ⅴ化合物半导体欧姆接触的研究进展

本文全面、系统地评述了A~ⅢB~Ⅴ化合物半导体材料上欧姆接触的研究现状和发展方向。首先考虑金属／半导体接触物理，从理论上阐明了欧姆接触的机理，以及对其表征和测试。其次，文章用大量篇幅，总结了利用不同方法（如重掺技术、金属化和能带工程等）实现各种A~ⅢB~Ⅴ半导体材料上欧姆接触的工艺过程、实验研究和重要结论，其中以GaAs最为详细。结合器件的发展和实际工艺的要求，文章还分析了各种制备方法的优缺点，并指出这方面研究工作目前存在的、急需解决的一些问题。     

Investigation of microstructure and chemical composition of Ni contacts to n-type 4H–SiC

Structure and chemical compositions of the interface layer obtained after nickel deposition on silicon carbide surface and subsequent annealing have been analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray diffraction (XRD) and Raman spectroscopy. Nickel silicide (Ni₂Si) were characterized as the main product of reaction between nickel and silicon carbide after annealing at temperatures range 700–1000 °C. Raman spectroscopy and TOF-SIMS profiling results confirmed carbon precipitation within contact layer. Obtained results indicate graphitic form of carbon and its non-uniform distribution in the contact layer. Moreover, TOF-SIMS analysis showed modification of nitrogen distribution in the contact area upon Ni/SiC contact annealing.     

AuGeNi—n型GaAs欧姆接触界面微区结构与接触电阻率的关系

欧姆接触是砷化镓器件中的基本单元，它的电性能极大地影响器件的质量。在众多的欧姆接触系统中，ＡｕＧｅＮｉ系统应用最为广泛。利用扫描俄歇电子微探针对离子注入重掺杂的ｎ型ＧａＡｓ上利用快速热合金制备的ＡｕＧｅＮｉ欧姆接触进行了研究，比较了不同退火温度下欧姆接触的电性能和微区界面结构，对界面微区结构与接触电阻的关系进行了探讨，提出了产生低阻接触的理想微区结构，为工艺参数的选择提供了有益的依据。     

表面处理对n-GaN上无合金化Ti/Al欧姆接触的作用

本文研究了表面处理对n-GaN上无合金化的Ti/Al电极起的作用,比较了(NH4)2Sx和CH3CSNH2两种不同的表面处理方法.在用CH3CSHN2/NH4OH溶液处理过的样品上制作的无合金化的Ti/Al电极,可得到较低的(4.85～5.65)×10-4Ω·cm2的接触电阻率,而且材料的发光特性也有明显提高.     

2.5GDFB量子阱激光器p型欧姆接触电极的研究

对2.5GDFB量子阱激光器p型低阻欧姆接触电极进行了研究,在退火温度400℃,退火时间30s进行快速热退火条件下,对Au-Pt-Ti/InAs/p+-InGaAs(掺Zn>1×1019cm-3)/MQW/n-InP和Au-Pt-Ti/p+-InGaAs(掺Zn>1×1019cm-3)/MQW/n-InP两种结构进行了p型欧姆接触试验研究,并对两者串联电阻进行了比较,其结果前者的串联电阻阻值为后者的1/4.     

Improved Al/Si ohmic contacts to p-type 4H-SiC

An AlSi-based ohmic contact with a new composition is reported in this paper. AlSi(2%)Ti(0.15%) contacts are formed by evaporation on p-type 4H-SiC grown by liquid phase epitaxy (LPE) and annealed in the temperature range from 700 to 950°C. The ohmic behaviour has been checked by I–V characteristics and the contact resistivity has been measured by the linear transmission-line-model (TLM) method. The dependence of the contact resistivity on the annealing conditions has been studied. An ohmic behaviour has been established at 700°C while the lowest contact resistivity value of 9.6×10⁻⁵ Ω cm² has been obtained after annealing at 950°C. The thermal stability of both Al/Si/SiC and AlSiTi/SiC contacts at a temperature of 600°C has been studied. It has been found that the AlSiTi/SiC contacts are stable for 100 h at this ageing temperature while the Al/Si/SiC contacts deteriorate after 24 h.